The present invention relates to an inhaler for delivery of medicament by inhalation, particularly but not exclusively to a breath-actuated inhaler.
Inhalers are commonly used for delivery of a wide range of medicaments. The inhaler houses a canister of medicament which is actuated to deliver a dose of medicament through a mouthpiece. Desirably the canister is replaceable so that the inhaler is re-useable after the canister is empty or can be used with different medicaments. However, this advantage can create safety problems. In particular, it is difficult to control the type of medicaments supplied by inhalers. For example, users might insert a canister containing an inappropriate medicament as different medicaments are commonly supplied in similar canisters. Users might not know whether a given inhaler which comes to hand will deliver the desired medicament. Such problems are particularly serious when the inhaler is needed to provide a particular medicament urgently in an emergency. The present invention is intended to improve safety in an inhaler with a replaceable canister.
According to the present invention, there is provided an inhaler for delivering medicament by inhalation, comprising a housing having a mouthpiece and defining an air flow path extending from the mouthpiece through the housing; the housing holding a replaceable canister of medicament actuatable to deliver a dose of medicament into the air flow path, wherein the housing defines an opening in the air flow path and the opening is closed by a closure element connected to and replaceable with the canister.
The closure element acts as a safety feature because it is only closed when the inhaler is used with a canister to which a closure element is connected. This enables better control over the type of medicament to be delivered in that valid canisters can be provided with closure elements connected thereto. The absence of the closure element may be recognised by the user on insertion.
Advantageously, the closure element carries an indication of the type of medicament in the canister. In this way, the closure element may provide the advantage that it enables the type of medicament to be easily recognised by a user. It is particularly advantageous that the indication is provided on an element connected to the cannister itself so the risk of confusion is reduced.
The indication may be printed information, such as different colours, patterns, text or numbers or the colour of the closure element itself. Desirably, the indication is a tactile surface, for example an embossed or indented pattern. This enables a user with poor eyesight to recognise the type of medicament, which would not otherwise be possible, particularly in the case of an indication visible, say, through a window.
Preferably, the opening is defined in the outer surface of the housing. This enables the presence or absence of the closure element to be clearly visible to a user of the inhaler with the canister fitted.
Desirably, the opening is provided adjacent the mouthpiece. This allows for the closure element to be easily formed with a connection to the canister which itself is normally adjacent the mouthpiece to enable engagement in a nozzle block directing medicament out of the mouthpiece. Also it assists in making the indication visible because in normal use the inhaler will be held with the mouthpiece in view, facing the user.
The safety may be improved further if the present invention is applied to a breath-actuated inhaler further comprising an actuation mechanism arranged to be operated to actuate the canister by a flow through the air flow path, the opening being arranged, when open, to vent the flow sufficiently to prevent operation of the actuation mechanism. In this way, the inhaler will not provide medicament if inserted with a canister without a closure element, potentially containing inappropriate medicament, or if a canister is inserted in the incorrect position. This improves safety and gives the inhaler provider better control over the proper use of the inhaler.
The opening may be positioned and dimensioned to prevent operation at in the absence of a closure element at an inhalation level above the maximum expected flow rate at the mouthpiece. For example, operation may be prevented at a flow rate of at least eight times a standard inhalation flow rate. Conversely, it is unnecessary for the closure element when present to completely close the opening, provided that it closes the opening sufficiently to allow operation of the inhaler.
Typically in a breath-actuated inhaler wherein the actuation mechanism includes a trigger disposed in the air flow path responsive to the flow to cause operation of the actuation mechanism, for example by comprising a pre-loading mechanism arranged to store a loading force for actuation of the canister, the trigger being arranged to release the stored force.
The trigger is preferably a vane arranged to be physically moved by a flow through the air flow path, although an electronic trigger sensing the flow is a conceivable alternative.
The present invention is particularly suited to a common, simple form of breath actuated inhaler in which wherein the housing has outer walls defining a space which constitutes the air flow path.
Desirably, the opening is disposed in the air flow path between the trigger and the mouthpiece. This is an advantageous structure, because the inhalation flow generated by inhalation at the mouthpiece is drawn through the opening without thereby limiting the flow created within the air flow path at the trigger to prevent operation of the trigger.
Preferably the housing defines an inlet opening for the air flow path having a smaller opening area than the opening. This increases the air flow resistance at the opening relative to the opening which assists in ensuring the inhalation flow is vented by the opening in preference to the inlet opening, hence allowing the opening to prevent operation of the actuation mechanism.
According to a second aspect of the present invention, there are provided a plurality of inhalers according to the first aspect wherein each given inhaler has an opening with a different shape and has a closure element with a shape which conforms with the opening of the given inhaler but which does not conform with the openings of the other inhalers.
This provides the inhalers with a form of canister recognition. Inhalers are to be used exclusively with canisters having a closure element with a conforming opening. Use of canisters in inhalers which do not have a conforming opening may be recognised by the different shapes and may be prevented by the shapes of the opening and the closure element of a given inhaler prevent fitting of the closure element in an inhaler other than the given inhaler. Alternatively, the different shapes may the inhalers further comprise an actuation mechanism arranged to be operated to actuate the canister by a flow through the air flow path and the shape of the closure element of a given inhaler is such that when the closure element fitting in inhaler other than the given inhaler leaves open the opening of the other inhaler sufficiently open to prevent operation of the actuation mechanism of the other inhaler.
Accordingly the second aspect of the present invention makes it possible to control the use of canisters in particular inhalers. For example, the different shapes of opening and closure elements may be used for respective types of medicament to reduce the chances of cross-contamination between inhalers for differing medicaments.
With either aspect of the present invention, the canister and the closure element are connected by a connector which is arranged to prevent reconnection after separation of the canister and the closure element, for example by the connector is formed with a weak portion arranged to be broken in preference to the remainder of the connector on application of a force to separate the canister and the closure element. This further enhances the security of the present invention because it prevents a closure element from a valid canister being removed and attached to a new canister.
To allow a better understanding, an inhaler which embodies the present invention will now be described by way of non-limitative example with reference to the accompanying drawings, in which: